As part of an ongoing program of study of the physicochemical properties of interacting macromolecules in solution, it is proposed to continue and extend our investigations into: (a) the interaction of chlorpromazine (Thorazine) with mouse brain tubulin in order to gain insight into the molecular mechanism of action of this tranquilizing drug; (b) the solution conformation of bradykinin, its analogs and model compounds as probed by the methods of CD and 13C-NMR; and (c) the solution conformation of luteinizing hormone releasing hormone as probed by CD. The chlorpromazine-tubulin interaction will be studied by the combined application of molecular sieve chromatography, ultracentrifugation and CD. In addition, it is proposed to initiate a theoretical study of the equilibrium sedimentation of interacting systems.